One common application of moveable frame assemblies is found on recreational vehicles and manufactured housing units. Because the maximum allowable width of recreational vehicles is limited by the width of the roads and highways, many recreational vehicles are equipped with one or more slide out rooms. These slide out rooms can be retracted into the main living quarters when the recreational vehicle is moved, and can then be extended from the main living quarters to provide auxiliary living space when the recreational vehicle is parked for use.
The moveable frames used to support these slide out rooms need to be kept in precise alignment relative to the fixed frame of the recreational vehicle in order to ensure that the moveable frame extends and retracts smoothly. Unfortunately, because slide out rooms are heavy and rather cumbersome, the rooms are liable to twist slightly as they are extended or retracted, which causes the room to bind or get stuck, thus damaging the room, the support system, or the hydraulic cylinders typically used to move the room. Therefore, in order to prevent these problems, either the forces used to extend or retract the slide out room must be equally applied to both sides of the frame, or the forces must be somehow synchronized so that both ends of the moveable frame move in tandem, such that the moveable frame remains parallel to and aligned with the fixed frame at all times.
A variety of synchronization and alignment systems have been used in the past, ranging from rack and pinion systems to cable and pulley arrangements. Each of the prior art alignment systems require a great deal of space underneath the vehicle, such as between the two main rails that form the frame of the vehicle. Unfortunately, the space between the main rails is typically occupied by storage tanks, heating ducts, plumbing, wiring, cross braces, and other obstructions. Furthermore, this space is frequently enclosed by an "underbelly" that protects the above items from dust, road grime, and the weather, and consequently the installation, adjustment, and maintenance of the alignment and synchronization systems is greatly impeded. Also, because the enclosed space sometimes is heated, systems that penetrate the space cause heat loss and provide an avenue for dust, dirt, and moisture to penetrate the protected area.
Some prior art systems use a pair of hydraulic cylinders to extend and retract the slide out room, which divides the force between two attachment points. However, a complex system of valves is required in order to ensure that the two cylinders extend and retract in unison. The use of two hydraulic cylinders and the need for valves to synchronize the cylinders greatly increases the installation and maintenance costs of such a system. Thus, the prior art alignment systems are expensive, difficult to fabricate and install, difficult to maintain, and prone to alignment and stability problems. Accordingly, there exists a need for an alignment mechanism that is more reliable and easier to install and maintain than are the systems referred to above.
The alignment and synchronization mechanism of the present invention is designed to alleviate the problems outlined above. The present invention utilizes two extensible members that are pivotally connected to each other in scissors type fashion, and which connect the moveable frame to the fixed frame. Each extensible member has a hollow outer leg and an extending inner leg that is telescopically disposed within the hollow outer leg when the moveable frame is in a folded or retracted position. The inner legs gradually extend out of their corresponding outer legs as the moveable frame is moved away from the fixed frame, which in effect lengthens each extensible member as the slide out room is extended and the moveable frame moves away from the fixed frame. The extension or retraction of the inner legs, as well as the unfolding or folding of the outer legs, are synchronized by a central pinion that connects the two extensible legs to each other. As the slide out room is extended, the pinion gradually feeds both inner legs out of their outer legs at the same rate. When the slide out room is retracted, the pinion ensures that the inner legs retract back into the outer legs at the same rate. The pinion engages a rack on each of the inner legs, and thus any movement of one inner leg produces a corresponding movement of the other inner leg. The pinion engages slots in the outer legs, which ensures that the outer legs fold and unfold at the same rate. Thus, as the extensible legs pivot towards or away from the fixed frame both legs are always at an equal angle relative to the fixed frame, which keeps the moveable frame parallel to the fixed frame at all times, and which prevents the moveable frame from moving forward or backward relative to the fixed frame. Furthermore, the synchronizing mechanism of the present invention operates independently of the system used to support the slide out room, and therefore the present invention can be used on any of the prior art room support systems.
The present invention is also much more stable than existing mechanisms such as the conventional scissors type mechanisms. On conventional scissors mechanisms having four attachment points, one of the attachment points on each of the fixed frame and the moveable frame must be slotted so that the attachment points can slide closer together as the frame is extended, which effectively makes the frame narrower and less rigid. By comparison, on the present invention all of the attachments are pin type connections, which are more precise and loss prone to wear than are slotted connections. Also, by virtue of the extensible legs, the synchronizing mechanism of the present invention has a wide stance that does not narrow as the room is extended, and thus the slide out room is very stable in all positions.
Furthermore, because none of the attachment points on the present invention are slotted, the central pivot point on the synchronizing mechanism does not move forward or backward relative to the fixed frame as the room is extended or retracted. Accordingly, the hydraulic cylinder does not need to pivot relative to the frame but instead can be rigidly mounted to the fixed frame which reduces wear and tear. Finally, in one embodiment of the present invention a drive rack carried by the hydraulic cylinder connects directly to and drives the synchronizing pinion. By virtue of the extensible legs, the moveable frame thus travels further than the stroke of the piston, which allows the use of a smaller, more compact, and less expensive hydraulic cylinder.
Accordingly, it is an object of this invention to provide an improved synchronization mechanism for slide out rooms.
It is another object of this invention to provide a synchronization mechanism that equally divides the force used to extend and/or retract the slide out room between two attachment points.
It is another object of this invention to provide a synchronizing mechanism having extensible legs which are power driven by a short stroke hydraulic cylinder.
A further object of this invention is to provide a synchronization mechanism having a pair of extensible legs synchronized by a central pinion such that any movement of one leg produces a corresponding movement in the other leg.
These and other objects of the invention will become readily apparent to those skilled in the art upon a reading of the following description.